MIAMI — The San Antonio Spurs have three more chances to grab the championship trophy that slipped away last year.

The way they’re dominating the Miami Heat, they might need just one.

Kawhi Leonard had 20 points and 14 rebounds, and the Spurs routed the Heat again, winning 107-86 on Thursday night to open a commanding 3-1 lead in the NBA Finals.

The Spurs can win their fifth NBA championship with a victory at home in Game 5 on Sunday and avenge their seven-game loss to Miami last year. And if the Heat are going to deny them again, it will take the biggest comeback in NBA Finals history.

“I’m pleased that they performed as well as they did while we’ve been in Miami, and that’s about as far as it goes,” Spurs coach Gregg Popovich said. “Now we’ve got to go back home and play as well or better.”

LeBron James tried to keep the Heat in it with 28 points and eight rebounds, but Dwyane Wade was just 1 of 10 through three quarters and finished with 10 points.

No team has overcome a 3-1 deficit in the finals, and the way they were outclassed twice on their home floor makes it hard to imagine the two-time champions being the first.

Tony Parker added 19 points, and Tim Duncan had 10 points and 11 rebounds for the Spurs, who shot 57 percent from the field.

The Spurs lost twice in Miami to end last year’s finals, their only defeat in the championship round. They won their two games in South Florida this time by a combined 40 points.

If this was the last home game of the season in Miami, it looked and sounded nothing like the ones to end the last two years, which featured confetti falling and trophies raised. This one had the unfamiliar sound of boos late in the first half and a chant of “Go Spurs Go!” with under 3 minutes left from the San Antonio fans who remained long after many of Miami’s had bolted.

If the Heat force a Game 6, it would be in Miami Tuesday.

The Heat had followed their last 13 postseason losses with a victory, but at the end of a fourth straight season that went the distance, they might be out of gas. Miami seemed to lack the energy — or maybe effort — to defend San Antonio’s precision ball movement for the full 24 seconds, and time after time the Spurs ended up with a shot from somebody who didn’t have a defender nearby.

Not quite as sharp as when they shot a finals-record 75.8 percent in the first half Tuesday night, the Spurs were still plenty good enough to open another huge lead by halftime, and they withstood every attempt Miami made to make a run.

“We were expecting a reaction from them but we were ready for it, so we just did the same thing,” Spurs forward Boris Diaw said.

The Spurs knew their defense had to be better, realizing their once-in-a-lifetime, 19-for-21 start in Tuesday’s 111-92 Game 3 victory covered the fact that they allowed Miami to make more than 50 percent in the game.

The defense was definitely improved in the first half, holding Miami to 12 of 34 (35 percent).

The Spurs missed their first three shots after needing 22 attempts to miss three times Tuesday. They quickly got untracked from there, running off a 13-2 spurt to open a nine-point lead, and that was the margin when they went to the second ahead 26-17.

San Antonio got the first five of the second to make it 31-17 on Danny Green’s 3-pointer, and the Spurs blew it open later in the quarter with seven straight points, capped by Leonard’s soaring follow dunk that made it 55-33.

It was another rough start for James, who battled cramps in Game 1, then left the court and briefly returned to the locker room midway through the first quarter Thursday.

He had 10 quick points in the third quarter to bring Miami within 13, but San Antonio got a basket from Duncan to start a 7-0 run that pushed it to 68-48. The Spurs poured it on late in the third, pushing the lead to 81-57.

Notes: Under Popovich, the Spurs have won 15 of the 18 best-of-seven series in which they led 2-1. ... The Heat hadn’t lost back-to-back games in the playoffs since dropping three straight against the Boston Celtics in the 2012 Eastern Conference finals.